Polycarbonate composite material which can be thermoplastically shaped, methods for the production thereof, use of the same and a flame-proof polycarbonate moulded part

ABSTRACT

The invention relates to a polycarbonate composite material which can be thermoplastically shaped and which comprises at least two layers. The invention is characterised in that at least one layer comprises an LOI value of lower than 29 and at least one layer comprises an LOI value of higher than 29. The invention also relates to methods for producing said material, the use of the same and flame-proof polycarbonate moulded parts.

[0001] The present invention relates to thermoplastically moldablecomposite polycarbonate materials, processes for their production, useof the materials, and flame-retardant polycarbonate moldings. Theinvention relates in particular to thermoplastically moldable compositepolycarbonate materials which can be used to produce flame-retardantpolycarbonate moldings with an attractive and functional surface effect.

[0002] Polycarbonate moldings have been known for a long time. They arewidely used in the sectors of electrical engineering and electronics(production of plugs, plug connectors, switches, component housings,printed circuit boards, distribution boxes, etc.), data processing(optical data-storage disks), lighting (lamp covers, lamp housings,illuminated placards, optical waveguide systems), optics (opticallenses, which can be rendered scratch-resistant via coatings), householdtechnology (housings for kitchen machines, fans, vacuum cleaners;microwave-resistant tableware, etc.), the leisure industry (safetyhelmets, fracture-proof protective goggles), the construction industry(translucent roofing, soundproof barriers), and vehicle construction[interior trim for buses, railroad cars and aircraft, dashboards, lampcovers, shock absorbers (made from polycarbonate blends, e.g. with ABS),and bodywork parts] (CD Römpp Chemie Lexikon [Römpp ChemicalEncyclopedia]—Version 1.0, Stuttgart/New York: Georg Thieme Verlag1995).

[0003] The self-extinguishing property of polycarbonates is not adequatein many application sectors. For example, for applications in aircraftconstruction polycarbonates have to meet particularly stringent fireprotection regulations, to comply with which they have hitherto requiredthe addition of flame retardants and/or flame-retarding additives. Dueto the presence of the flame retardants and/or the flame-retardingadditives, these polycarbonate moldings become non-transparent, andgenerally acquire a slight to marked unintended color.

[0004] The consumer demands that the visible side of polycarbonatemoldings be attractive. In the case of flame-retarding grades, this iscurrently achieved by means of opaque coloration and, where appropriate,structuring of the surface.

[0005] The colors produced here are preferably plain colors, for reasonsassociated with extrusion technology. Some of the surfaces of themoldings are decorated by using specific, flame-retarding lacquers. Adisadvantage of this procedure is that these lacquering processes arevery complicated, and that it is impossible to achieve many of thedesired surface effects and functional surface effects. Furthermore, thedecorative finishes applied have inadequate protection from mechanicaleffects.

[0006] In the light of the prior art, it was then an object of thepresent invention to provide a thermoplastically moldable compositepolycarbonate material which permits the production of flame-retardantpolycarbonate moldings with an attractive and functional surface effect,where these moldings are not restricted to plain colors. In particular,it should be possible to produce flame-retardant polycarbonate moldingsnot hitherto disclosed, with functional surface effects.

[0007] Another object consists in providing a thermoplastically moldablecomposite polycarbonate material which satisfies current fire protectionregulations, in particular those of the aircraft industry. Thethermoplastically moldable composite polycarbonate material should becapable of simple, low-cost production.

[0008] Another object on which the present invention was based was toprovide a process which can be carried out at low cost and is capable oflarge-scale application, to produce the thermoplastically moldablecomposite polycarbonate material of the invention. In addition, theprocess should be easy and simple to carry out using commerciallyavailable components.

[0009] Another object of the invention was to provide a polycarbonatemolding with attractive and functional surface effects. This surfaceeffect should have protection from external effects, such asenvironmental effects and mechanical effects. Possible uses of thepolycarbonate molding of the invention should also be given.

[0010] These objects are achieved, as are other objects not explicitlymentioned but readily derivable or deducible from the circumstancesdescribed in the introduction to this specification, by means of athermoplastically moldable composite polycarbonate material with all ofthe features of claim 1. Useful modifications of the thermoplasticallymoldable composite polycarbonate material of the invention are protectedby the subclaims dependent on claim 1. Processes for producing thethermoplastically moldable composite polycarbonate material of theinvention are described in the process claims. In addition, aflame-retardant polycarbonate molding is claimed, obtainable from thethermoplastically moldable polycarbonate molding via thermoplasticmolding. The use claim protects a preferred use of the flame-retardantpolycarbonate molding of the invention.

[0011] The provision of a thermoplastically moldable compositepolycarbonate material with at least two layers, where the material hasat least one layer with an LOI value smaller than 29 and at least onelayer with an LOI value greater than 29, is a successful and not readilyforeseeable method of obtaining a thermoplastically moldable compositepolycarbonate material with an attractive and functional surface effect.It enables simple production of a polycarbonate molding with anattractive and functional surface effect, on a large scale and at lowcost. Surface effects which are novel and have not previously beendisclosed can be achieved here.

[0012] The fact that thermoplastic molding can be used to obtain aflame-retardant polycarbonate molding from a thermoplastically moldablecomposite polycarbonate material with at least two layers, where thematerial has at least one layer with an LOI value smaller than 29 and atleast one layer with an LOI value greater than 29 is particularlysurprising because polycarbonates with an LOI value smaller than 29 donot comply with the usual fire-protection regulations, in particular inthe aircraft construction sector. At the same time, other advantages areachievable via the process of the invention. They include:

[0013] There is no need to lacquer the surfaces of the thermoplasticallymoldable composite material of the invention and of the molding whichcan be produced therefrom.

[0014] The surface effect of the invention of the thermoplasticallymoldable composite material of the invention and of the molding whichcan be produced therefrom has protection from mechanical effects.

[0015] The present invention provides thermoplastically moldablepolycarbonates. Polycarbonates are plastics known to the skilled worker.They represent thermoplastic polymers having the general structuralformula

[0016] and can be formally regarded as polyesters made from carbonicacid and from an aliphatic or aromatic dihydroxy compound. The radical Rhere represents bivalent aliphatic, cycloaliphatic, or aromatic groupswhich derive from the corresponding dihydroxy compounds.

[0017] Polycarbonates which may be used according to the inventioninclude homopolycarbonates, copolycarbonates, unbranched polycarbonates,branched polycarbonates, and mixtures of the polycarbonates mentioned.

[0018] For the purposes of the present invention, preference is given toaromatic radicals R. These include radicals which derive fromhydroquinone, from resorcinol, from 4,4′-dihydroxydiphenol, from2,2-bis(4-hydroxyphenyl)propane, from2,4-bis(4-hydroxyphenyl)-2-methylbutane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, from2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, from2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, or from1,1-bis(4-hydroxyphenyl)cyclohexane, or from1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane. Particularlypreferred radicals R are derived from 2,2-bis(4-hydroxyphenyl)propane orfrom 1,1-bis(4-hydroxyphenyl)cyclohexane.

[0019] Where appropriate, the radicals R may bear other substituents,preferably methyl groups or halogen groups. Particularly preferredsubstituents are bromine atoms and chlorine atoms.

[0020] The polycarbonates of the invention preferably have aweight-average molar mass in the range from 10 000 g/mol to 200 000g/mol. Particular preference is given to a weight-average molar mass inthe range from 10 000 g/mol to 100 000 g/mol, in particular from 15 000g/mol to 45 000 g/mol.

[0021] The polycarbonates of the invention may comprise other polymersmiscible with polycarbonate. These include poly(meth)acrylates,polyesters, polyamides, polyimides, polyurethanes, polyethers, ABS, ASA,and PBT.

[0022] For the purposes of the present invention, miscibility of thevarious substances means that the components form a homogeneous mixture.

[0023] The polycarbonates may moreover comprise additives well known inthe technical field. These include antistats, antioxidants, dyes,fillers, light stabilizers, pigments, UV absorbers, agents providingweathering protection, and plasticizers.

[0024] According to the present invention, the thermoplasticallymoldable composite polycarbonate material has at least two layers whichdiffer in their LOI value. The term “layer” is well known to the skilledworker. For the purposes of the present invention, layers representregions of homogeneous LOI value, delineated from one another and fromthe surroundings by sharp boundaries. For the purposes of the presentinvention, the shape of the layers is as desired. The layer shapespreferred according to the invention are obtainable by means ofextrusion.

[0025] According to the invention, at least one layer of thethermoplastically moldable composite polycarbonate material has an LOIvalue smaller than 29 and at least one layer has an LOI value greaterthan 29. The LOI value is an abbreviation known to the skilled workerfor what is called the oxygen index (being derived from the term“limiting oxygen index”), and this value states the limiting value foroxygen usage in an oxygen/nitrogen mixture at which the material justcontinues to burn independently after ignition by an external flame. Itis usually determined using the ASTM D 2863 test method. Straightpolycarbonate in which no flame retardant or flame-retarding additivesare present usually has an LOI value of 26. The LOI value can beincreased to 32-35 by adding flame retardants and/or flame-retardingadditives (Bodo Carlowitz Kunststofftabellen [Plastics tables] 4thedition; Munich, Vienna; Hanser 1995 p. 146).

[0026] Flame retardants and/or flame-retarding additives are known tothe skilled worker. They represent those inorganic and/or organicsubstances which are intended to provide flameproofing (flameretardancy) in particular to wood and wood-based materials, plastics,and textiles. They achieve this by inhibiting the spread of flame to thesubstances to be protected, impeding ignition, and making combustionmore difficult. Flame retardants and/or flame-retarding additivesencompass, inter alia, substances whose action comprises suffocating thefire, promoting carbonization, and forming a barrier layer and/or aninsulating layer. They include specific inorganic compounds, such asaluminum oxide hydrates, aluminum hydroxides, water glass, borates, inparticular zinc borates, antimony oxide (mostly together with organichalogen compounds), ammonium phosphates, such as (NH₄)₂HPO₄, andammonium polyphosphates.

[0027] Other flame-retarding additives or flame retardants which may beused according to the invention encompass halogenated organic compounds,such as chloroparaffins, hexabromobenzene, brominated diphenyl ethers,and other bromine compounds, organophosphorus compounds, especiallyphosphates, phosphites, and phosphonates, in particular those withplasticizer action, such as triscresyl phosphate, and halogenatedorganophosphorus compounds, such as tris(2,3-dibromopropyl) phosphate ortris(2-bromo-4-methylphenyl) phosphate.

[0028] The flame-retarding additives and/or flame retardants which maybe used according to the invention moreover also include thosesubstances which expand in the manner of a foam on heating, carbonize atfrom 250° C. to 300° C., and in the process become solid and form afine-pored cushion providing good insulation; examples being mixtures ofurea, dicyandiamide, melamine, and organic phosphates.

[0029] The flame retardants and/or flame-retarding additives may beadded to the polycarbonate before its preparation is complete. It isalso possible to incorporate flame-retarding compounds in the form ofmonomers into the polycarbonate macromolecules.

[0030] Preference is given to those flame retardants and/orflame-retarding additives which in the event of fire do not form anyenvironmentally hazardous substances, such as toxic phosphates andhigh-toxicity dioxins.

[0031] In one preferred embodiment of the present invention, the atleast one layer with an LOI value smaller than 29 has an LOI valuesmaller than 28, preferably smaller than 27.

[0032] In another preferred embodiment of the present invention, the atleast one layer with an LOI value greater than 29 has an LOI valuegreater than 30, preferably greater than 31.

[0033] For the purposes of the present invention, the at least one layerwith an LOI value greater than 29 is preferably obtainable from amixture composed of

[0034] a) from 40 to 100% by weight, based on the total weight of themixture, of at least one polycarbonate

[0035] b) from 0 to 40% by weight, based on the total weight of themixture, of at least one polymer from the group consisting ofpoly(meth)acrylates, polyesters, polyamides, polyimides, polyurethanes,polyethers, ABS, ASA, and PBT

[0036] c) from 0 to 10% by weight, based on the total weight of themixture, of at least one flame retardant and/or flame-retarding additive

[0037] d) from 0 to 10% by weight, based on the total weight of themixture, of at least one additive from the group consisting ofantistats, antioxidants, dyes, fillers, light stabilizers, pigments, UVabsorbers, agents providing weathering protection, and plasticizers,

[0038] where the entirety of a), b), c), and d) gives 100% by weight.

[0039] It is also preferable that the at least one layer with an LOIvalue smaller than 29 is obtainable from a mixture composed of

[0040] e) from 40 to 100% by weight, based on the total weight of themixture, of at least one polycarbonate

[0041] f) from 0 to 40% by weight, based on the total weight of themixture, of at least one polymer from the group consisting ofpoly(meth)acrylates, polyesters, polyamides, polyimides, polyurethanes,polyethers, ABS, ASA, and PBT

[0042] g) from 0 to 10% by weight, based on the total weight of themixture, of at least one additive from the group consisting ofantistats, antioxidants, dyes, fillers, light stabilizers, pigments, UVabsorbers, agents providing weathering protection, and plasticizers,

[0043] where the entirety of e), f), and g) gives 100% by weight.

[0044] The number of layers in the thermoplastically moldable compositepolycarbonate material of the invention depends on the desired field ofapplication. The thermoplastically moldable composite polycarbonatematerial of the invention here is composed of at least 2 layers,preferably of 2, 3, 4, or 5 layers.

[0045] Certain properties of the thermoplastically moldable compositepolycarbonate material of the invention, in particular itscombustibility, may be influenced via the ratio of the thickness of theat least one layer with an LOI value smaller than 29 and the thicknessof the at least one layer with an LOI value greater than 29. This ratiois preferably in the range from 0.01 to 0.5.

[0046] The ratio of the weight of the at least one layer with an LOIvalue smaller than 29 and the weight of the at least one layer with anLOI value greater than 29 can also influence some of the properties ofthe thermoplastically moldable composite polycarbonate material of theinvention, in particular its combustibility. This ratio is preferablylikewise in the range from 0.01 to 0.5.

[0047] In one preferred embodiment of the present invention, the atleast one polycarbonate layer with an LOI value smaller than 29 has athickness of from 30 μm to 500 μm. For the purposes of the presentinvention, it is also preferable for the at least one polycarbonatelayer with an LOI value greater than 29 to have a thickness of from 0.7mm to 3 mm.

[0048] For the purposes of the present invention, preference is given toa thermoplastically moldable composite polycarbonate material in which apolycarbonate layer with an LOI value smaller than 29 is an outer layerof the composite polycarbonate material.

[0049] In one particularly preferred embodiment of the presentinvention, the thermoplastically moldable composite polycarbonatematerial has, between a layer with an LOI value greater than 29 and alayer with an LOI value smaller than 29, a third layer, the third layerbeing a decorative layer.

[0050] The skilled worker will clearly see that the thermoplasticallymoldable composite polycarbonate material of the invention may also havefurther layers. For example, it may have further polycarbonate layerswhose composition differs from that of the abovementioned layers. It mayhave further decorative layers or print layers. The thermoplasticallymoldable composite polycarbonate material may moreover also compriseadhesive layers which may serve either to bond layers made from variousplastics or else to secure the films onto the articles to be protected.There may also be variation in the layer sequence.

[0051] The thermoplastically moldable composite polycarbonate materialof the invention meets the most stringent fire-protection requirements,in particular those from the aircraft construction sector. Therequirements of the American authorities have binding effect worldwideon the air travel industry sector (FAR, Part 25, Amdt. 25-72, App. F,Part I (b) (4), Vertical Test; App. F., Part I (b) (5), HorizontalTest). Depending on the application sector, for example wall sheetingand ceiling sheeting, cables, and lines, the requirement is todemonstrate limited spread of fire and limited afterflame time for thetest specimen, and in some cases the absence of combustion of drippings.In this context, FAR (FAR 25.853 (a) (1) (i), (ii), (iv), or (v))requires that a flame be applied horizontally from the side orvertically from beneath to an elongate specimen (in the shape of astrip; 305 mm×75 mm). According to the invention, preference is given tothe vertical flame application test.

[0052] In order to meet current requirements, when a flame is applied tothe edge of the test specimen for 60 and 12 seconds, respectively, theafterflame time must not exceed 15 seconds and the burn length must notbe more than 150 and 200 mm, respectively, and the flame time ofdrippings must be smaller than 3 and 5 seconds, respectively,

[0053] In one preferred embodiment of the present invention, on verticalflame-application to an edge for 60 seconds in accordance with FAR25.853 (a) (1) (i) the thermoplastically moldable compositepolycarbonate material of the present invention has a burn lengthsmaller than 150 mm, preferably smaller than 120 mm, and the afterflametime is shorter than 15 seconds, preferably shorter than 9 seconds, andthe flame time of drippings is smaller than 3 seconds, preferablysmaller than 2 seconds.

[0054] For the purposes of the present invention, preference is alsogiven to thermoplastically moldable composite polycarbonate materialswhich, on vertical flame-application to an edge for 12 seconds inaccordance with FAR 25.853 (a) (1) (ii), have a burn length smaller than200 mm, preferably smaller than 50 mm, where the afterflame time isshorter than 15 seconds, preferably shorter than 7 seconds, and theflame time of drippings does not exceed 5 seconds, preferably does notexceed 1 second.

[0055] The FAR and Airbus-Industrie require that materials for theinterior fitting of aircraft also comply with certain limitingNBS-chamber smoke density values (FAR 25.853 (c); AITM 2.0007) (FAR,Part 25, Amdt. 25-72, App. F, Part V: Test Method to determine the SmokeEmission Characteristics of Cabin Materials) (Airbus Industrie TechnicalSpecification ATS-1000.001, Issue 5; Airbus Directives ABD0031). In thistest, a square test specimen (74 mm±1 mm×74 mm±1 mm) arranged verticallyin the NBS chamber is irradiated by an electrical source of radiatedheat with I=25 kW/m², and thus pyrolytically decomposed. A photometersystem is used to measure the attenuation of a light beam due to smokeparticles released, as a function of time. The test is carried out for 6minutes under smoldering conditions (without ignition flame) or withignition flame. The specific optical density to be calculated must notbe above Ds_(max)=200 during a test period of four minutes.

[0056] In one preferred embodiment of the present invention, a featureof the thermoplastically moldable composite polycarbonate material isthat the specific optical density in accordance with FAR 25.858 (c) andAITM 2.0007 does not exceed Ds_(max)=200, preferably does not exceedDs_(max)=140, during a test period of four minutes.

[0057] The toxicity of the fire gases is evaluated in accordance withthe Airbus specification AITM 3.0005 (Airbus Industrie TechnicalSpecification ATS-1000.001, Issue 5; Airbus Directives ABD0031) usinganalytically determined concentration values for various smokecomponents during the NBS chamber test. The current limiting values hereaccording to ATS are 3 500 ppm for carbon monoxide CO, 100 ppm forsulfur dioxide SO₂, 150 ppm for hydrogen chloride HCl, 150 ppm forhydrogen cyanide HCN, 100 ppm for hydrogen fluoride, and 100 ppm for thenitrogen-containing gases nitrogen monoxide NO and nitrogen dioxide NO₂.

[0058] According to the invention, preference is given tothermoplastically moldable composite polycarbonate materials for whichthe fire gases during the NBS chamber test in accordance with AITM3.0005 comprise not more than 3 500 ppm, preferably not more than 300ppm, of carbon monoxide, not more than 100 ppm of sulfur dioxide,preferably no sulfur dioxide, not more than 100 ppm of hydrogenchloride, preferably no hydrogen chloride, not more than 150 ppm,preferably not more than 2 ppm, of hydrogen cyanide, not more than 100ppm of hydrogen fluoride, preferably no hydrogen fluoride, and not morethan 100 ppm, preferably not more than 3 ppm, of nitrogen monoxide andnitrogen dioxide.

[0059] Processes for producing the thermoplastically moldable compositepolycarbonate material of the invention will be apparent to the skilledworker. For the purposes of the present invention, a preferred processis extrusion. This begins by using at least two dry polycarbonate mixeswhich, where appropriate, comprise other components, at least one drymix with an LOI value greater than 29 and at least one dry mix with anLOI value smaller than 29.

[0060] For the purposes of the invention, dry mixing means that duringthe further course of the process there is no need to remove solventfrom this mixture. Permissible solvent residues are those for which nofurther treatment is needed or which can be separated from the mixtureby vacuum in the extruder. The dry mix preferably comprises less than0.01% by weight of solvent, based on the total weight of the dry mix.

[0061] The mixing may take place in conventional apparatus well knownfor this purpose. The temperature at which the mixing takes place isbelow the gelling temperature of the respective mixture. This step ispreferably carried out at room temperature.

[0062] The dry mix with an LOI value smaller than 29 is separatelyextruded onto a polishing stack, the temperature of whose rollers isbelow 140° C., thus molding a film. The extrusion of polymers to givefilms or layers is well known, and is described by way of example inKunststoffextrusionstechnik II [Plastics extrusion technology II],Hanser Verlag, 1986, pp. 125 et seq. Extrusion may take place by way ofwhat is known as the “chill roll” method, of which FIG. 1 gives adiagram. The hot melt is passed from the die of the extruder 1 onto achill roll 2, polished rollers being used to obtain high gloss. However,the process of the invention may also use rollers other than a chillroll. A further roller 3 then takes up the melt cooled on the roller 2,thus giving a single-layer film 4, which can be provided with furtherlayers. As an alternative, the extrusion process may also take place ina polishing stack, as in the diagram of FIG. 2. Here, the hot melt iscalendered between two or more rollers 3 to give continuous films 4.

[0063] In order that the film produced is substantially free fromcontamination, a filter is arranged upstream of entry of the melt intothe die. The mesh width of the filter generally depends on the startingmaterials used, and may correspondingly vary over a wide range. However,it is generally in the range from 300 μm to 20 μm. Filters with two ormore screens of different mesh widths may also be arranged upstream ofthe entry to the die. These filters are well known in the technicalfield and are commercially available. The examples attached can alsoserve as a further starting point for the skilled worker.

[0064] In order to obtain high-quality films it is moreover advantageousto use particularly pure raw materials. The thickness of each film orlayer may vary across a wide range which generally depends on thedesired use. As mentioned above, the preferred thickness of at least onefilm or layer with an LOI value smaller than 29 is from 30 μm to 500 μm,and the preferred thickness of at least one film or layer with an LOIvalue greater than 29 is between 0.7 mm and 3 mm. The film thickness orlayer thickness may be adjusted via parameters which are known to theskilled worker.

[0065] The pressure used to press the molten mixtures into therespective dies may be controlled, by way of example, via the screwspeed. The pressure is generally in the range from 40 to 100 bar, butthis is not intended to restrict the process of the invention. Theexamples attached will give the skilled worker further indications inrelation to the general process parameters.

[0066] So that the resultant films or layers have high surface qualityand low haze, it is important that the temperature selected for the dieis higher than the temperature of the mixture upstream of entry to thedie, but lower than the gelling temperature.

[0067] The die temperature is preferably set higher by 5%, particularlypreferably by 10%, and very particularly preferably by 15%, than thetemperature of the mixture upstream of entry to the die.Correspondingly, preferred die temperatures are in the range from 283°C. to 345° C., particularly preferably from 297° C. to 345° C., and veryparticularly preferably from 310° C. to 345° C.

[0068] The film to be laminated onto the material is producedseparately, where appropriate printed, and then laminated to the basesubstrate in the polishing stack.

[0069] In one preferred embodiment of the present invention, the surfaceof at least one film or layer with an LOI value smaller than 29 isprovided with an optical effect. The film provided with the opticaleffect and having an LOI value smaller than 29 is then laminated to afilm or layer with an LOI value greater than 29 in such a way that theresultant thermoplastically moldable composite polycarbonate materialhas at least one decorative layer between a layer with an LOI valuesmaller than 29 and a layer with an LOI value greater than 29.

[0070] The application of these layers by co-lamination may take placeat room temperature or at a slightly elevated temperature, avoiding anyimpairment of the surface quality and the haze of the layers. Theseprocesses are well known in the technical field and are described by wayof example in Kunststoffextrusionstechnik II [Plastics extrusiontechnology II], Hanser Verlag, 1986, pp. 320 et seq.

[0071] For the purposes of the present invention, it is particularlyadvantageous that the abovementioned steps, i.e. the production of thepolycarbonate-containing films or polycarbonate-containing layers, and,where appropriate, the printing and the lamination to other layers,generally be carried out in a continuous process.

[0072] The result is a sheet product from which polycarbonate moldingscan be thermoformed. Thermoforming is a process known to the skilledworker for producing polymer moldings by molding the desired moldingsfrom a thermoplastically moldable polymer above a certain temperature.“Molding” here encompasses all of the activities which alter the shapeof the moldable polymer, examples being mono- and biaxial stretching,and also the manufacture of specific moldings. For the purposes of thepresent invention, the thermoplastically moldable composite material ispreferably hot-molded at a temperature above 165° C.

[0073] Possible application sectors for the polycarbonate molding of theinvention will be apparent to the skilled worker. It is particularlysuitable for any of the applications for which single- or multilayerpolycarbonate moldings are suitable. Their characteristic propertiesmake them particularly suitable for applications in sectors which haveto comply with stringent fire-protection requirements, in particular forapplications in aircraft construction.

[0074] The examples below and the comparative example serve toillustrate the invention, but are not intended to result in anyrestriction.

COMPARATIVE EXAMPLE 1

[0075] A commercially available, flame-retardant, black-coloredpolycarbonate (e.g. MAKROLON®) with one smooth and one structured sidewas used. The thickness of the material was 2.0 mm. The polycarbonatehad an LOI value of 32-35 to ASTM D 2863.

[0076] a) Flame Application Tests

[0077] In accordance with FAR 25.853 (a) (1), a flame was applied to anelongate specimen (strip; 305 mm×75 mm), horizontally from the side orvertically from below, for 60 or 12 seconds. The tests here wererepeated 3 times. The results are given in tables 1 to 4, where they arecompared with the current permitted limiting values. TABLE 1 Flameapplication to comparative example 1; 60 s vertical; FAR 25.853 (a) (1)(i) Afterflame time in Burn length in [s] Longitudinal [mm] SpecimenDrippings 1 75 2 0 2 80 0 0 3 70 0 0 4 75 1 0 5 70 7 6 Average 74 2 1Limiting value 152 15 3

[0078] TABLE 2 Flame application to comparative example 1; 60 shorizontal; FAR 25.853 (a) (1) (iv) Afterflame time in Burn length in[s] Transverse [mm] Specimen Drippings 1 70 0 0 2 80 3 0 3 70 0 0 4 65 40 5 75 0 0 Average 72 1 0 Limiting value 152 15 3

[0079] TABLE 3 Flame application to comparative example 1; 12 svertical; FAR 25.853 (a) (1) (ii) Afterflame time in Burn length in [s]Longitudinal [mm] Specimen Drippings 1 10 2 0 2 15 2 0 3 15 2 0 4 15 3 05 15 3 0 Average 14 2 0 Limiting value 203 15 5

[0080] TABLE 4 Flame application to comparative example 1; 12 shorizontal; FAR 25.853 (a) (1) (v) Afterflame time in Burn length in [s]Transverse [mm] Specimen Drippings 1 15 2 0 2 15 1 0 3 10 2 0 4 15 3 0 515 2 0 Average 14 2 0 Limiting value 152 15 3

[0081] b) Smoke Density Measurements

[0082] In accordance with FAR 25.853 (c) and AITM 2.0007, a square testspecimen (74 mm±1 mm×74 mm±1 mm), vertically arranged in a NBS chamber,was irradiated with an electric source of radiated heat with I=25 kW/m²,and thus pyrolytically decomposed. A photometer system was used tomeasure the attenuation of a light beam due to smoke particles released,as a function of time. The test was carried out for 6 minutes undersmoldering conditions with ignition flame. The values calculated for thespecific optical density are given in table 5, and are compared with thecurrent limiting value for thermoplastic moldings Ds_(max)=200 (during atest period of four minutes). TABLE 5 Smoke density test with flameapplication to comparative example 1; FAR 25.853 (c) Optical density attime t in [min] Ds max Specimen 1 1.5 2 3 4 5 6 within 4 min 1 4 19 4567 89 109 122 89 2 8 24 36 73 92 117 137 92 3 5 20 39 77 105 122 141 1054 5 18 43 67 84 92 102 84 Average 6 20 41 71 93 110 126 93 Limitingvalue to FAR 25.853 (c) 200

[0083] c) Smoke Analysis

[0084] In accordance with AITM 3.0005, the smoke in the NBS chamber wasanalyzed using calorimetric analysis tubes. The results are given intable 6 and compared with the current ATS limiting values. TABLE 6 Smokeanalysis from comparative example 1; AITM 3.0005 Limiting value inDetected in [ppm] Gas component [ppm] after 4 min after 4 min HCN 1500.0 CO 3 500 200 NO + NO₂ 100 0.5 SO₂ + H₂S 100 0.0 HF 100 ./. HCl 150./.

EXAMPLE 1

[0085] A commercially available, flame-retardant, gray-coloredpolycarbonate (e.g. MAKROLON®) with one smooth and one structured sidewas used (thickness of material: 1.2 mm), to the structured side ofwhich a non-flame-retardant polycarbonate film (thickness: 80 μm) hadbeen laminated. The flame-retardant polycarbonate had an LOI value of32-35 to ASTM D 2863, and the non-flame-retardant polycarbonate had anLOI value of 26 to ASTM D 2863.

[0086] a) Flame application tests

[0087] Method as in comparative example 1, results in tables 7 to 10TABLE 7 Flame application to example 1; 60 s vertical; FAR 25.853 (a)(1) (i) Afterflame time in Burn length in [s] Longitudinal [mm] SpecimenDrippings 1 95 10 0 2 105 15 0 3 105 3 5 4 100 0 0 5 100 2 0 Average 1016 1 Limiting value 152 15 3

[0088] TABLE 8 Flame application to example 1; 60 s horizontal; FAR25.853 (a) (1) (iv) Afterflame time in Burn length in [s] Transverse[mm] Specimen Drippings 1 100 2 0 2 100 0 0 3 105 3 15 4 115 9 0 5 100 60 Average 104 4 3 Limiting value 152 15 3

[0089] TABLE 9 Flame application to example 1; 12 s vertical; FAR 25.853(a) (1) (ii) Afterflame time in Burn length in [s] Longitudinal [mm]Specimen Drippings 1 15 1 0 2 15 2 0 3 20 1 0 4 15 3 0 5 20 2 0 Average17 2 0 Limiting value 203 15 5

[0090] TABLE 10 Flame application to example 1; 12 s horizontal; FAR25.853 (a) (1) (v) Afterflame time in Burn length in [s] Transverse [mm]Specimen Drippings 1 15 0 0 2 20 3 0 3 20 2 0 4 20 4 0 5 15 1 0 Average18 2 0 Limiting value 152 15 3

[0091] b) Smoke Density Measurements

[0092] Method as in comparative example 1, results in table 11 TABLE 11Smoke density test with flame application to example 1; FAR 25.853 (c)Optical density at time t in [min] Ds max Specimen 1 1.5 2 3 4 5 6within 4 min 1 8 28 55 75 82 87 92 82 2 13 33 46 65 92 105 113 92 3 5 3659 75 84 87 92 84 4 4 17 29 47 62 75 87 62 Average 8 29 47 66 80 89 9680 Limiting value to FAR 25.853 (c) 200

[0093] c) Smoke Analysis

[0094] Method as in comparative example 1, results in table 12 TABLE 12Smoke analysis from example 1; AITM 3.0005 Limiting value in Detected in[ppm] Gas component [ppm] after 4 min after 4 min HCN 150 0.5 CO 3 500200 NO + NO₂ 100 0.5 SO₂ + H₂S 100 0.0 HF 100 ./. HCl 150 ./.

EXAMPLE 2

[0095] A commercially available, flame-retardant, gray-coloredpolycarbonate (e.g. MAKROLON®) with one smooth and one structured sidewas used (thickness of material: 2.0 mm), the structured side of whichhad been laminated to a non-flame-retardant polycarbonate film(thickness: 90 μm). The flame-retardant polycarbonate had an LOI valueof 32-35 to ASTM D 2863, and the non-flame-retardant polycarbonate hadan LOI value of 26 to ASTM D 2863.

[0096] a) Flame Application Tests

[0097] Method as in comparative example 1 (vertical tests only), resultsin tables 13 and 14 TABLE 13 Flame application to example 2; 60 svertical; FAR 25.853 (a) (1) Afterflame time in (i) Burn length in [s]Longitudinal [mm] Specimen Drippings 1 50 7 0 2 55 2 0 3 60 9 0 4 60 7 05 60 1 0 Average 57 5 0 Limiting value 152 15 3

[0098] TABLE 14 Flame application to example 2; 12 s vertical; FAR25.853 (a) (1) (ii) Afterflame time in Burn length in [s] Longitudinal[mm] Specimen Drippings 1 20 2 0 2 20 1 0 3 20 1 0 4 20 2 0 5 20 0 0Average 20 1 0 Limiting value 203 15 5

[0099] b) Smoke Density Measurements

[0100] Method as in comparative example 1, results in table 15 TABLE 15Smoke density test with flame application to example 2; FAR 25.853 (c)Optical density at time t in [min] Ds max Specimen 1 1.5 2 3 4 5 6within 4 min 1 6 26 50 89 109 127 132 109 2 3 11 26 59 82 98 117 82 3 525 60 102 113 122 127 113 4 3 14 54 113 167 175 175 167 Average 4 19 4891 118 131 138 118 Limiting value to FAR 25.853 (c) 200

[0101] c) Smoke Analysis

[0102] Method as in comparative example 1, results in table 16 TABLE 16Smoke analysis from example 2; AITM 3.0005 Limiting value in Detected in[ppm] Gas component [ppm] after 4 min after 4 min HCN 150 0.5 CO 3 500200 NO + NO₂ 100 0.5 SO₂ + H₂S 100 0.0 HF 100 ./. HCl 150 ./.

EXAMPLE 3

[0103] A commercially available, flame-retardant, gray-coloredpolycarbonate (e.g. MAKROLON®) with one smooth and one structured sidewas used (thickness of material: 1.0 mm), the structured side of whichhad been laminated to a non-flame-retardant polycarbonate film(thickness: 175 μm). The flame-retardant polycarbonate had an LOI valueof 32-35 to ASTM D 2863, and the non-flame-retardant polycarbonate hadan LOI value of 26 to ASTM D 2863.

[0104] a) Flame Application Tests

[0105] Method as in example 2 (vertical tests only), results in tables17 and 18 TABLE 17 Flame application to example 3; 60 s vertical; FAR25.853 (a) (1) (i) Afterflame time in Burn length in [s] Longitudinal[mm] Specimen Drippings 1 80 8 0 2 85 7 0 3 85 2 0 4 90 2 0 5 75 4 0Average 83 5 0 Limiting value 152 15 3

[0106] TABLE 18 Flame application to example 3; 12 s vertical; FAR25.853 (a) (1) Afterflame time in (ii) Burn length in [s] Longitudinal[mm] Specimen Drippings 1 95 10 0 1 25 2 0 2 25 4 0 3 25 3 0 4 25 10 0 525 2 0 Average 25 4 0 Limiting value 203 15 5

[0107] b) Smoke Density Measurements

[0108] Method as in comparative example 1, results in table 19 TABLE 19Smoke density test with flame application to example 3; FAR 25.853 (c)Optical density at time t in [min] Ds max Specimen 1 1.5 2 3 4 5 6within 4 min 1 23 30 34 55 67 77 84 67 2 16 35 47 65 79 89 98 79 3 16 2633 54 59 69 79 59 4 14 25 40 77 95 109 122 95 Average 17 29 39 63 75 8696 75 Limiting value to FAR 25.853 (c) 200

[0109] c) Smoke Analysis

[0110] Method as in comparative example 1, results in table 20 TABLE 20Smoke analysis from example 3; AITM 3.0005 Limiting value in Detected in[ppm] Gas component [ppm] after 4 min after 4 min HCN 150 0.0 CO 3 500180 NO + NO₂ 100 0.5 SO₂ + H₂S 100 0.0 HF 100 ./. HCl 150 ./.

EXAMPLE 4

[0111] A commercially available, flame-retardant, gray-coloredpolycarbonate (e.g. MAKROLON®) with one smooth and one structured sidewas used (thickness of material: 2.0 mm), the structured side of whichhad been laminated to a non-flame-retardant polycarbonate film(thickness: 500 μm). The flame-retardant polycarbonate had an LOI valueof 32-35 to ASTM D 2863, and the non-flame-retardant polycarbonate hadan LOI value of 26 to ASTM D 2863.

[0112] a) Flame Application Tests

[0113] Method as in example 2 (vertical tests only), results in tables21 and 22 TABLE 21 Flame application to example 4; 60 s vertical; FAR25.853 (a) (1) (i) Afterflame time in Burn length in [s] Longitudinal[mm] Specimen Drippings 1 50 0 0 2 45 1 0 3 50 1 0 4 45 1 0 5 45 5 0Average 47 2 0 Limiting value 152 15 3

[0114] TABLE 22 Flame application to example 4; 12 s vertical; FAR25.853 (a) (1) (ii) Afterflame time in Burn length in [s] Longitudinal[mm] Specimen Drippings 1 10 1 0 2 10 3 0 3 10 2 0 4 10 4 0 5 10 2 0Average 10 2 0 Limiting value 203 15 5

[0115] b) Smoke Density Measurements

[0116] Method as in comparative example 1, results in table 23 TABLE 23Smoke density test with flame application to example 4; FAR 25.853 (c)Optical density at time t in [min] Ds max Specimen 1 1.5 2 3 4 5 6within 4 min 1 13 30 50 84 138 147 143 138 2 9 23 35 53 67 75 84 67 3 1131 43 75 122 141 157 122 4 14 29 42 71 98 109 113 98 Average 12 28 43 71106 118 124 106 Limiting value to FAR 25.853 (c) 200

[0117] c) Smoke Analysis

[0118] Method as in comparative example 1, results in table 24 TABLE 24Smoke analysis from example 4; AITM 3.0005 Limiting value in Detected in[ppm] Gas component [ppm] after 4 min after 4 min HCN 150 0.0 CO 3 500100 NO + NO₂ 100 1.5 SO₂ + H₂S 100 0.0 HF 100 ./. HCl 150 ./.

What is claimed is:
 1. A thermoplastically moldable compositepolycarbonate material with at least two layers, characterized in thatat least one layer has an LOI value smaller than 29 and at least onelayer as an LOI value greater than
 29. 2. The thermoplastically moldablecomposite polycarbonate material as claimed in claim 1, characterized inthat the at least one layer with an LOI value greater than 29 isobtainable from a mixture composed of a) from 40 to 100% by weight,based on the total weight of the mixture, of at least one polycarbonateb) from 0 to 40% by weight, based on the total weight of the mixture, ofat least one polymer from the group consisting of poly(meth)acrylates,polyesters, polyamides, polyimides, polyurethanes, polyethers, ABS, ASA,and PBT c) from 0 to 10% by weight, based on the total weight of themixture, of at least one flame retardant and/or flame-retarding additived) from 0 to 10% by weight, based on the total weight of the mixture, ofat least one additive from the group consisting of antistats,antioxidants, dyes, fillers, light stabilizers, pigments, UV absorbers,agents providing weathering protection, and plasticizers, where theentirety of a), b), c), and d) gives 100% by weight.
 3. Thethermoplastically moldable composite polycarbonate material as claimedin claim 1 or 2, characterized in that the at least one layer with anLOI value smaller than 29 is obtainable from a mixture composed of e)from 40 to 100% by weight, based on the total weight of the mixture, ofat least one polycarbonate f) from 0 to 40% by weight, based on thetotal weight of the mixture, of at least one polymer from the groupconsisting of poly(meth)acrylates, polyesters, polyamides, polyimides,polyurethanes, polyethers, ABS, ASA, and PBT g) from 0 to 10% by weight,based on the total weight of the mixture, of at least one additive fromthe group consisting of antistats, antioxidants, dyes, fillers, lightstabilizers, pigments, UV absorbers, agents providing weatheringprotection, and plasticizers, where the entirety of e), f), and g) gives100% by weight.
 4. The thermoplastically moldable compositepolycarbonate material as claimed in at least one of the precedingclaims, characterized in that it is composed of 2, 3, 4, or 5 layers. 5.The thermoplastically moldable composite polycarbonate material asclaimed in at least one of the preceding claims, characterized in thatthe ratio of the thickness of the at least one layer with an LOI valuesmaller than 29 and the thickness of the at least one layer with an LOIvalue greater than 29 is in the range from 0.01 and 0.5.
 6. Thethermoplastically moldable composite polycarbonate material as claimedin at least one of the preceding claims, characterized in that the ratioof the weight of the at least one layer with an LOI value smaller than29 and the weight of the at least one layer with an LOI value greaterthan 29 is in the range from 0.01 to 0.5.
 7. The thermoplasticallymoldable composite polycarbonate material as claimed in at least one ofthe preceding claims, characterized in that the at least onepolycarbonate layer with an LOI value smaller than 29 has a thickness offrom 30 μm to 500 μm.
 8. The thermoplastically moldable compositepolycarbonate material as claimed in at least one of the precedingclaims, characterized in that the at least one polycarbonate layer withan LOI value greater than 29 has a thickness of from 0.7 mm to 3 mm. 9.The thermoplastically moldable composite polycarbonate material asclaimed in at least one of the preceding claims, characterized in that apolycarbonate layer with an LOI value smaller than 29 is an outer layerof the composite polycarbonate material.
 10. The thermoplasticallymoldable composite polycarbonate material as claimed in at least one ofthe preceding claims, characterized in that, between a layer with an LOIvalue greater than 29 and a layer with an LOI value smaller than 29, ithas a third layer, the third layer being a decorative layer.
 11. Thethermoplastically moldable composite polycarbonate material as claimedin at least one of the preceding claims, characterized in that when itis subject to vertical flame application to an edge for 60 seconds inaccordance with FAR 25.853 (a) (1) (i) it has a burn length smaller than150 mm, and the afterflame time is shorter than 15 seconds, and theflame time of drippings is smaller than 3 seconds.
 12. Thethermoplastically moldable composite polycarbonate material as claimedin at least one of the preceding claims, characterized in that thespecific optical density in accordance with FAR 25.853 (c) and AITM2.0007 does not exceed Ds_(max)=200 during a test period of fourminutes.
 13. A process for producing a thermoplastically moldablecomposite polycarbonate material as claimed in at least one of thepreceding claims, characterized in that a) at least one dry mix with anLOI value smaller than 29 and at least one dry mix with an LOI valuegreater than 29 are extruded, and b) the resultant films and, whereappropriate, other films are laminated to one another to obtain thethermoplastically moldable composite material.
 14. A process forproducing a thermoplastically moldable composite polycarbonate materialas claimed in at least one of the preceding claims, characterized inthat a) the surface of at least one film with an LOI value smaller than29 is provided with an optical effect, and then b) the film providedwith the optical effect and with an LOI value smaller than 29 islaminated to a film with an LOI value greater than 29 in such a way thatthe resulting thermoplastically moldable composite polycarbonatematerial has at least one decorative layer between a layer with an LOIvalue smaller than 29 and a layer with an LOI value greater than
 29. 15.A flame-retardant polycarbonate molding obtainable by a process in whicha thermoplastically moldable composite polycarbonate material as claimedin at least one of claims 1 to 12 is thermoplastically molded.
 16. Theuse of a thermoplastically moldable polycarbonate composite as claimedin claim 15 in the aircraft construction sector.